1. Field of the Invention
Push pin fasteners for use in securing heat sinks to printed circuit boards and/or other components to cool heat-generating electric devices mounted to the component.
2. Description of Related Art
As shown in FIG. 1, plastic push pins 10 with bifurcated barbed ends 12 are known for use in mounting heat sinks to electric circuit boards containing heat generating devices. When such pins are inserted into mounting holes on one side of a circuit board, the bifurcated ends will compress until they extend through the hole to the other side of the circuit board, whereupon the ends will return to their normal position and the barbs engage the other side of the board. A drawback of such pins is that the barbed ends may be abraded or break off during insertion or during use of the device, whereupon the pins will no longer stay in place.
As shown in FIG. 2, plastic push pins also exist with stoppers or plungers 14, wherein the stopper is depressed when the pins are in place in the circuit board. When the stopper is depressed, the distal end (which is not bifurcated or otherwise split) is maintained in an expanded condition. Such known pins are also provided with a coil spring 16 on the outside of the pin to provide an opposing force in a direction opposite of the pin insertion direction to assist in engagement of the distal end against the circuit board and thereby provide a clamping force between an intermediate structure through which the pin passes and the circuit board. A drawback, however, is that the plastic material is still subject to breakage during, for example, shock and vibration testing.
Metal (e.g., brass) push pins with bifurcated ends are considered more robust than plastic pins as the barbs that grab the back side of the printed circuit board are stronger than plastic barbs. A problem, however, is that variation in the designs (slot length, square or radius slot end), difference in material properties (yield strength), and other factors like minor differences in the printed circuit board hole size have allowed failures to occur with metal push pins as well.